MURINE DENDRITIC CELLS PULSED IN-VITRO WITH TOXOPLASMA-GONDII ANTIGENS INDUCE PROTECTIVE IMMUNITY IN-VIVO

The activation of a predominant T-helper-cell subset plays a critical role in disease resolution, In the case of Toxoplasma gondii, the avai lable evidence indicates that CD4(+) protective cells belong to the Th 1 subset. The aim of this study was to determine whether T. gondii ant igens (in T. gondii sonicate [TSo]) presented by splenic dendritic cel ls (DC) were able to induce a specific immune response in vivo and to protect CBA/J mice orally challenged with T.gondii cysts. CBA/J mice i mmunized with TSo-pulsed DC exhibited significantly fewer cysts in the ir brains after oral infection,vith T.gondii 76K than control mice did . Protected mice developed a strong humoral response in vivo, with esp ecially high levels of anti-TSo immunoglobulin G2a antibodies in serum . T,gondii antigens such as SAG1 (surface protein), SAG2 (surface prot ein), MIC1 (microneme protein), ROP2 through ROP4 (rhoptry proteins), and MIC2 (microneme protein) were recognized predominantly. Furthermor e, DC loaded with TSo, which synthesized high levels of interleukin-12 (IL-12), triggered a strong cellular response in vivo, as assessed by the proliferation of lymph node cells in response to TSo restimulatio n in vitro. Cellular proliferation was associated with gamma interfero n and IL-2 production. Taken together, these results indicate that imm unization of CBA/J mice with TSo-pulsed DC can induce both humoral and Th1-like cellular immune responses and affords partial resistance aga inst the establishment of chronic toxoplasmosis.